Why && operator isn't necessary in this code?

Get Help JavaScript
#1

I don’t understand why && operator isn’t necessary when you want to fulfill the conditions below.

Here’s how it’s supposed to calculate the relationship:

100 should return 'You are likely identical twins.'
35-99 should return 'You are likely parent and child or full siblings.'
14-34 should return 'You are likely grandparent and grandchild, aunt/uncle and niece/nephew, or half siblings.'
6-13 should return 'You are likely 1st cousins.'
3-5 should return 'You are likely 2nd cousins.'
1-2 should return 'You are likely 3rd cousins.'
0 should return 'You are likely not related.'

const whatRelation = percentSharedDNA => {
    if (percentSharedDNA === 100) {
        return 'You are likely identical twins.'
    }
    if (percentSharedDNA > 34) {
        return 'You are likely parent and child or full siblings.'
    }
    if (percentSharedDNA > 13) {
        return 'You are likely grandparent and grandchild, aunt/uncle and niece/nephew, or half siblings.'
    }
    if (percentSharedDNA > 5) {
        return 'You are likely 1st cousins.'
    }
    if (percentSharedDNA > 2) {
        return 'You are likely 2nd cousins.'
    }
    if (percentSharedDNA > 0) {
        return 'You are likely 3rd cousins'
    }
    return 'You are likely not related.'
}

For  me, for instance,
if (percentSharedDNA > 34 && percentSharedDNA < 100) {
        return 'You are likely parent and child or full siblings.'

seems to work well.
1 Like
#2

It’s because it does all of these in order. If it were not for the order, then you’re right, you’d need && to set the boundaries on each one.

In the check if it’s over 34, if it’s also 100, your function already exited with the return statement in the first if conditon.
Similarly, in the check if it’s over 13, if it’s also over 34, it already exited with one of the previous return statements.

1 Like